This application is based on Application No. 2001-093425, filed in Japan on Mar. 28, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a stator and a stator core used in a dynamoelectric machine such as an automotive alternator and a method for manufacture thereof, and particularly to a stator core construction.
2. Description of the Related Art
In a dynamoelectric machine such as an automotive alternator, reductions in size and increases in output are in demand. Various proposals have been made which attempt to achieve reductions in size and increases in output by raising the space factor of electrical conductors housed in magnetic circuits of stators, and in addition, by aligning in rows and increasing the density of coil ends of stator windings (crossover portions of a stator winding which are constructed at end surfaces of a stator core). Stator cores are normally prepared by laminating thin magnetic plates in the order of 0.3 to 1.0 mm in order to suppress core loss.
FIG. 16 is a perspective showing a conventional stator for an automotive alternator, FIG. 17 is a diagram explaining a method for manufacturing a stator winding used in the conventional stator for an automotive alternator, FIG. 18 is a perspective showing a laminated body constituting a stator core used in the conventional stator for an automotive alternator, FIG. 19 is a perspective showing the stator core used in the conventional stator for an automotive alternator, and FIGS. 20A to 20D are process cross sections explaining a method for mounting the stator winding to the stator core in the conventional stator for an automotive alternator.
Here, a method for manufacturing the conventional stator will be explained with reference to FIGS. 17 to 20D.
First, as shown in FIG. 17, an annular winding unit 2 is prepared by winding one strand of a conductor wire 1 coated with an electrical insulator for a predetermined number of winds, and a star-shaped winding unit 3 is prepared by forming the annular winding unit 2 into a star shape in which end portions of adjacent pairs of slot-housed portions 3a are alternately linked on an inner circumferential side and an outer circumferential side by linking portions 3b. 
Next, although not shown, thin magnetic plates of predetermined length are prepared by press forming a strip-shaped body composed of a magnetic material. A plurality of plate teeth are formed at a predetermined pitch in a longitudinal direction on the thin magnetic plates. Plate teeth at first and second ends are formed into two matching sections.
A laminated body 5 is prepared as shown in FIG. 18 by laminating a predetermined number of the thin magnetic plates 4 prepared in this manner such that the plate teeth are superposed, and integrating the laminated thin magnetic plates 4 by welding predetermined positions on an outer surface thereof (the surface on the opposite side from the teeth). Plate-joining weld portions 6 are formed over an entire width region of the laminated body 5 at positions that divide the longitudinal direction of the laminated body 5 into four sections (three positions), for example. Body slots 5a are defined by adjacent pairs of body teeth 5b. 
Next, the laminated body 5 is bent into an annular shape with openings of the body slots 5a facing an inner circumferential side to obtain a laminated core 7. First and second ends of the annular laminated core 7 are abutted and an outer circumferential surface of the abutted portion 7a is welded to obtain a cylindrical stator core 8, as shown in FIG. 19. A core-joining weld portion 10 is formed over an entire axial region on an outer circumferential surface of the stator core 8. In this stator core 8, one core-joining weld portion 10 and three plate-joining weld portions 6 are formed at an even angular pitch on the outer circumferential surface. Core slots 8a defined by adjacent pairs of core teeth 8b are formed so as to be arranged at an even angular pitch in a circumferential direction with slot grooves lying in an axial direction and slot openings facing an inner circumferential side.
Next, two of the star-shaped winding units 3 are stacked on top of one another such that the slot-housed portions 3a of each are mutually offset by three slots in a circumferential direction. The two star-shaped winding units 3 stacked on top of one another in this manner are set in a winding unit inserter as shown in FIG. 20A. The winding unit inserter is constituted by a core holder 11, a coil holder 12, axially-extending blades 13, a stopper 14, etc. Here, the stator core 8 is supported by the core holder 11 and the coil holder 12, the blades 13 being placed on an inner circumferential surface of the stator core 8 so as to open an opening portion of every third core slot 8a. The two stacked star-shaped winding units 3 are disposed at a lower end of the stator core 8 such that the slot-housed portions 3a thereof are stacked on top of one another in every third core slot 8a relative to the axial direction, and linking portions 3b on the inner circumferential side are positioned on an inclined surface 14a of the stopper 14.
Next, as the stopper 14 is moved upward in FIG. 20B by a driving means (not shown), the linking portions 3b on the inner circumferential side slide over the inclined surface 14a of the stopper 14, are shifted to an outer circumferential side, and eventually come into contact with an inner circumferential surface of the blades 13. As shown in FIGS. 20B and 20C, as the stopper 14 moves further upward, the linking portions 3b on the inner circumferential side move upward along the inner circumferential surface of the blades 13, and the slot-housed portions 3a move upward and gradually incline. Hence, the slot-housed portions 3a are guided by the blades 13 and are gradually housed in the core slots 8a from the opening portions of the core slots 8a. At this time, the linking portions 3b on the outer circumferential side are guided by the coil holder 12 and are gradually shifted upward and to the inner circumferential side. As shown in FIG. 20D, as the stopper 14 moves to tip ends of the blades 13, the linking portions 3b on the inner circumferential side are conveyed along the arc-shaped inner circumferential surface of the blades 13 to an upper end of the stator 8, and the slot-housed portions 3a are conveyed completely inside the core slots 8a. By this first star-shaped winding unit installation process, the two star-shaped winding units 3 are each installed in every third core slot 8a. 
Next, the stopper 14 is lowered and the blades 13 are rotated circumferentially by one slot. Hence, the blades 13 are placed on the inner circumferential surface of the stator core 8 so as to open an opening portion of every third core slot 8a in a group of slots in which the star-shaped winding units 3 are not yet installed. As above, two stacked star-shaped winding units 3 are disposed at the lower end of the stator core 8 such that the slot-housed portions 3a thereof are stacked on top of one another in every third core slot 8a relative to the axial direction, and the linking portions 3b on the inner circumferential side are positioned on the inclined surface 14a of the stopper 14. The stopper 14 is raised and the slot-housed portions 3a are conveyed inside the core slots 8a in a similar manner to the first star-shaped winding unit installation process above. By this second star-shaped winding unit installation process, the next two star-shaped winding units 3 are each installed into every third core slot 8a offset by one slot from those of the first star-shaped winding unit installation process. Similarly, a third star-shaped winding unit installation process is performed to install the remaining two star-shaped winding units 3 into every third core slot 8a offset by one slot from those of the second star-shaped winding unit installation process.
After installing the six star-shaped winding units 3 in this manner, a coil end shaping process is performed to prepare a stator 15 composed of a stator winding 9 installed in the stator core 8 as shown in FIG. 16. Distributed wave windings composed of two star-shaped winding units 3 installed in every third core slot 8a each constitute one winding phase portion. In other words, the stator winding 9 is constituted by a three-phase winding, each winding phase portion being constituted by a distributed wave winding.
Hence, because the conventional stator 15 is prepared by installing the stator winding 9 (the star-shaped winding units 3) in the cylindrical stator core 8, the installation operation for the stator winding 9 is complicated, and one problem has been that the rate of production of the stator 15 has been poor.
Thus, in order to improve the rate of production of the stator, as shown in FIG. 21, a method is proposed in Japanese Patent Non-Examined Laid-Open No. 9-103052, for example, in which flat plate-shaped winding units 16 are prepared by winding conductor wires 1 into a wave shape, and the stator is prepared by bending a rectangular parallelepiped laminated body 5 into an annular shape together with the flat plate-shaped winding units 16 after mounting the flat plate-shaped winding units 16 into the laminated body 5.
In the stator 15 used in the conventional automotive alternator, as described above, the stator core 8 is prepared by preparing the rectangular parallelepiped laminated body 5 in which a predetermined number of the thin magnetic plates 4 are laminated, preparing the laminated core 7 by bending the laminated body 5 into the annular shape, and abutting and welding the first and second circumferential ends of the laminated core 7. Stress when bending the laminated body 5 into the annular shape acts to offset first and second longitudinal ends of each of the thin magnetic plates 4 in a circumferential direction. However, in the conventional stator 15, because the plate joining weld portions 6 are formed on the outer surface of the laminated body 5 (the surface on the opposite side from the teeth) across the entire width region of the laminated body 5 in positions which divide the longitudinal direction of the laminated body 5 into four sections (three positions), for example, the thin magnetic plates 4 are not joined at the first and second longitudinal ends of the laminated body 5, and one problem has been that tooth tip surfaces at the first and circumferential ends of the laminated core 7 become irregular, as shown in FIGS. 22 and 23. Irregularities on the tooth tip surfaces arise easily at the axially-outer ends of the stator core 15.
Thus, one problem has been that when the stator winding 9 is installed in the stator core 8 prepared in this manner, the electrically-insulating coating on the conductor wires 1 is damaged by the irregularities on the tooth tip surfaces, making electrical insulation poor due to short-circuiting among the conductor wires 1 and to short-circuiting between the conductor wires 1 and the stator core 8.
Because welding is not applied to the inner circumferential surface of the stator core 8, turning up of the tooth tip ends occurs easily when the stator winding 9 is installed, particularly in the portions where irregularities have occurred on the tooth tip surfaces. Thus, another problem has been that this turning up of the tooth tip ends damages the electrically-insulating coating on the conductor wires 1 during installation of the stator winding 9 and also damages the electrically-insulating coating on the conductor wires 1 after installation, making electrical insulation poor due to short-circuiting among the conductor wires 1 and to short-circuiting between the conductor wires 1 and the stator core 8.
Although turning up of the tooth tip ends occurring when the stator winding 9 is installed can be prevented in the stator proposed as an improvement because the laminated body 5 is bent into an annular shape after mounting the laminated body 5 with the flat plate-shaped winding units 16, one problem has been that the conductor wires 1 of the flat plate-shaped winding units 16 are damaged by irregularities on the tooth tip surfaces arising during bending of the laminated body 5, making electrical insulation poor due to short-circuiting among the conductor wires 1 and to short-circuiting between the conductor wires 1 and the stator core 8.
This tendency toward deterioration in electrical insulation becomes more pronounced as the space factor of the electrical conductors is improved and as the density of the coil ends is increased due to reductions in the size of and increases in the output from dynamoelectric machines.
The present invention aims to solve the above problems and an object of the present invention is to provide a stator core for a dynamoelectric machine and a method for the manufacture thereof in which the generation of irregularities in tooth tip surfaces at first and second ends of a laminated body during bending of the laminated body is suppressed by applying plate-joining weld portions to outer surfaces and inner surfaces at first and circumferential ends of the laminated body in addition to plate-joining weld portions that are applied at positions on the outer surfaces of the laminated body that divide the longitudinal direction of the laminated body into a plurality of sections.
Another object of the present invention is to provide a stator for a dynamoelectric machine enabling suppression of deterioration of electrical insulation resulting from irregularities in the tooth tip surfaces.
In order to achieve the above object, according to one aspect of the present invention, there is provided a stator core for a dynamoelectric machine,
the stator core being formed into a cylindrical shape by abutting at least one laminated core division shaped by bending a rectangular parallelepiped laminated body;
the laminated body being formed by laminating a plurality of thin strip-shaped magnetic plates in which a plurality of teeth extending perpendicular to a longitudinal direction are formed at a predetermined spacing in the longitudinal direction; and
a plurality of slots defined by adjacent pairs of the teeth being formed in a circumferential direction of the stator core such that slot grooves lie in an axial direction of the stator core and slot openings face an inner circumferential side of the stator core,
wherein an inner and an outer core-joining weld portion for joining and integrating the abutted portion of the laminated core division are formed so as to extend in an axial direction on an inner circumferential side and an outer circumferential side of the abutted portion of the laminated core division,
first inner and first outer plate-joining weld portions for joining and integrating the laminated thin magnetic plates are formed so as to extend in the axial direction in proximity to the inner and outer core-joining weld portions on inner circumferential surfaces and outer circumferential surfaces at first and second circumferential end portions of the laminated core division, and
a second outer plate-joining weld portion for joining and integrating the laminated thin magnetic plates is formed so as to extend in an axial direction on an outer circumferential surface of the laminated core division.
Weld depths of the first inner and first outer plate-joining weld portions and the second outer plate-joining weld portion may vary relative to an axial direction.
The first inner plate-joining weld portions may be formed on inner circumferential surfaces of tips of the teeth.
The abutted portion of the laminated core division may be positioned on a circumferentially-central portion of one of the teeth, the first inner plate-joining weld portions being formed on mutually opposite sides of the inner core-joining weld portion on the tooth constituting the abutted portion.
Second inner plate-joining weld portions for joining and integrating the laminated thin magnetic plates may be formed so as to extend in an axial direction on inner circumferential surfaces of tips of all of the teeth except for the teeth on which the first inner plate-joining weld portions are formed.
A weld depth of the second inner plate-joining weld portion may vary relative to an axial direction.
The first and second outer plate-joining weld portions may be positioned radially outside the teeth.
According to another aspect of the present invention, there is provided a stator for a dynamoelectric machine including:
a cylindrical stator core in which a plurality of slots defined by adjacent pairs of teeth are formed in a circumferential direction such that slot grooves lie in an axial direction and slot openings face an inner circumferential side; and
a stator winding installed in the stator core,
wherein the stator core is formed into a cylindrical shape by abutting first and second circumferential end surfaces of a laminated core shaped by bending a rectangular parallelepiped laminated body into an annular shape, the laminated body being formed by laminating a plurality of thin strip-shaped magnetic plates in which a plurality of teeth extending so as to be perpendicular to a longitudinal direction are formed at a predetermined spacing in the longitudinal direction,
an inner and an outer core-joining weld portion for joining and integrating the abutted portion of the laminated core are formed so as to extend in an axial direction on an inner circumferential side and an outer circumferential side of the abutted portion of the laminated core,
first inner and first outer plate-joining weld portions for joining and integrating the laminated thin magnetic plates are formed so as to extend in the axial direction in proximity to the inner and outer core-joining weld portions on inner circumferential surfaces and outer circumferential surfaces at first and second circumferential end portions of the laminated core, and
a second outer plate-joining weld portion for joining and integrating the laminated thin magnetic plates is formed so as to extend in an axial direction on an outer circumferential surface of the laminated core.
Weld depths of the first inner and first outer plate-joining weld portions and the second outer plate-joining weld portion may vary relative to an axial direction.
The first inner plate-joining weld portions may be formed on inner circumferential surfaces of tips of the teeth.
The abutted portion of the laminated core may be positioned on a circumferentially-central portion of one of the teeth, the first inner plate-joining weld portions being formed on mutually opposite sides of the inner core-joining weld portion on the tooth constituting the abutted portion.
Second inner plate-joining weld portions for joining and integrating the laminated thin magnetic plates may be formed so as to extend in an axial direction on inner circumferential surfaces of tips of all of the teeth except for the teeth on which the first inner plate-joining weld portions are formed.
A weld depth of the second inner plate-joining weld portion may vary relative to an axial direction.
The first and second outer plate-joining weld portions may be positioned radially outside the teeth.
The rectangular parallelepiped laminated body may be shaped by bending into an annular shape with the stator winding mounted in the slots.
The stator winding may be installed such that a conductor wire alternately occupies an inner layer and an outer layer in a slot depth direction in the slots at intervals of a predetermined number of slots.
According to yet another aspect of the present invention, there is provided a method for manufacturing a stator core for a dynamoelectric machine including the steps of:
preparing thin magnetic plates of a predetermined length from a strip-shaped body composed of a magnetic material, a plurality of teeth being formed on the thin magnetic plates at a predetermined spacing;
preparing a rectangular parallelepiped laminated body by laminating a predetermined number of the thin magnetic plates such that the teeth are superposed on each other;
forming a second outer plate-joining weld portion by welding a predetermined position on an outer surface of the laminated body so as to extend across an entire width region of the outer surface, the outer surface being on an opposite side from the teeth;
forming first outer plate-joining weld portions by welding a vicinity of first and second longitudinal end portions on the outer surface of the laminated body so as to extend across an entire width region of the outer surface of the laminated body;
forming first inner plate-joining weld portions by welding a vicinity of first and second longitudinal end portions on an inner surface of the laminated body so as to extend across an entire width region of the inner surface of the laminated body;
preparing a laminated core division by bending the laminated body on which the first and the second outer plate-joining weld portions and the first inner plate-joining weld portions are formed; and
integrating the laminated core division into a cylindrical shape by abutting at least one of the laminated core divisions and welding an outer surface and an inner surface of the abutted portion thereof so as to extend across an entire axial region of the laminated core division.
The first inner plate-joining weld portions may be formed on inner circumferential surfaces of tips of the teeth.
The abutted portion of the laminated core division may be positioned on a circumferentially-central portion of one of the teeth, the first inner plate-joining weld portions being formed on mutually opposite sides of an inner core-joining weld portion formed by welding the inner surface of the abutted portion on the tooth constituting the abutted portion.
Second inner plate-joining weld portions may be formed by welding inner circumferential surfaces of tips of all of the teeth except for the teeth on which the first inner plate-joining weld portions are formed so as to extend across an entire axial region, formation of the second inner plate-joining weld portions being performed before preparing the laminated core division by bending the laminated body.